The present invention relates to an arrangement for a multi-cylinder internal-combustion engine having at least two intake valves per cylinder to which separate first and second intake pipes lead that are dimensioned differently with respect to length and/or cross-section and are each equipped with a fuel injection valve. A controllable flap is in at least the second intake pipe, this flap being opened and closed as a function of an operating state of the internal-combustion engine determined from operating conditions of the engine.
Because of the achievable higher volumetric efficiency, internal-combustion engines are frequently equipped with two intake valves for each cylinder. In order to fully utilize the performance yield that can be achieved by this technology, it is necessary to keep the intake pipes leading to the intake valves as short as possible. However, this has a negative influence on the torque characteristics of the internal-combustion engine in the lower rotational speed range so that an abundant course of the torque that is desirable in motor vehicle engines cannot be achieved in this rotational speed range. This range, in turn, requires suction pipes that are as long as possible which, however, limits the achievable performance yield at high rotational speeds.
For this reason, it was suggested in German Utility Model No. 1,986,850 to equip the two intake pipes leading to the two intake valves with different lengths and cross-sections, in which the shorter pipe, in the lower rotational speed range, is closed by a flap and is opened in the upper rotational speed range. However, this is a carburetor-type internal-combustion engine which in comparison to injection-type internal-combustion engines has the known disadvantages of the unfavorable injection site and therefore of the required mixture flow reversal of occurring fuel condensation at the suction pipe walls.
These known disadvantages can be avoided when a manifold injection is used for the mixture formation instead of a carburetor. In order to avoid an excessive stratifying of the charge, one injection valve is provided for each intake pipe. However, in this case, problems occur when the intake port for the full-load operation and its injection valve are connected because the flow conditions in the two intake pipes change with respect to one another during the connecting or disconnecting with the movement of the flap. It was therefore suggested in German Published Unexamined Patent Application No. 3,444,356 to control the injection valve by means of several injection pulses even before the complete opening or during the closing of the flap. However, here also, a faulty adaptation of the mixture occurs during the change-over phase because the intake mixture is adapted only incompletely to the changing flow conditions in the intake pipes.
It is therefore an objective of the present invention to carry out a fuel feed to a fuel-injected internal-combustion engine having two intake pipes for each cylinder so that a faulty adaptation of the mixture and/or a charge stratification during the opening and closing of a controllable flap is avoided in one of at least two intake ports.
This and other objectives are achieved in an arrangement for an engine having two intake valves per cylinder to which separate first and second intake pipes lead, by providing control means for apportioning between the intake pipes via the injection valves a total quantity of fuel fed to the cylinder during the opening and closing of the flap corresponding to flow conditions changing with movement of the flap in the intake pipes.
The main advantages of the invention are the fact that in the case of an internal-combustion engine that is equipped with at least two intake pipes and of which at least one can be closed via a flap, a faulty adaptation of the mixture and a stratification of the charge during the opening and closing of the flap is avoided in that a total amount of fuel that is to be fed to a cylinder, corresponding to the flow conditions that change with the movement of the flap in the intake pipes, via the respective injection valves, is apportioned to the two intake pipes.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.